This invention relates to methods and transfer elements for thermal transfer of layers, as well as the devices formed thereby. In particular, the invention relates to thermal transfer elements and methods for the thermal transfer of microstructured layers, as well as the devices formed thereby.
There is a general trend to reduce the size of many articles and devices used in industrial and consumer applications, particularly in electronics. In addition, a variety of articles and devices utilize modified surfaces. These articles and devices often require microstructured (and, in some instances, nanostructured) surfaces, layers, or components. For example, field emission devices used for articles, such as flat panel displays, can be formed using nanostructured elements (e.g., fibers, whiskers, or rods), as disclosed in U.S. Pat. No. 5,726,524, incorporated herein by reference. Nanostructured elements can also be used in, for example, catalyst systems, chemical sensors, and bioabsorption substrates. Microstructured surfaces and layers can be useful in, for example, electroluminescence devices, field emission cathodes for display devices, fluid control films having capillary channels, bioanalytical and biomolecular processing devices, and patterned electronic components and circuits.
In at least some instances, it is inconvenient, economically unfeasible, or difficult to form these microstructured and nanostructured elements, layers, surfaces, and components on a desired substrate. For example, the nanostructured elements of a field emission device may be difficult to form in a desired pattern on a substrate. Known techniques for patterning small features on substrates include, for example, ablation or adhesive lift-off techniques to remove a portion of a previously formed layer of microstructured or nanostructured elements. However, these methods may require multiple steps and may produce excessive waste materials.
Generally, the present invention relates to the formation of articles having a layer with a surface defining microstructured features, as well as thermal transfer elements and methods for making the articles. One embodiment is a thermal transfer element including a microstructured layer having a surface defining microstructured features imposed on the microstructured layer. The thermal transfer element is configured and arranged for the transfer of at least a portion of the microstructured layer to a receptor while substantially preserving the microstructured features of that portion. The thermal transfer element can include one or more additional layers such as, for example, a light-to-heat conversion layer, an interlayer, a release layer, and an adhesion layer.
Another embodiment is a method of making an article. A receptor substrate of the article is contacted with a thermal transfer element having a microstructured layer including a surface defining microstructured features imposed on the microstructured layer. At least a portion of the microstructured layer is then selectively transferred to the receptor substrate while substantially preserving the microstructured features of that portion. The transfer can be performed by selectively applying a heating element or by selectively illuminating an optional light-to-heat conversion layer of the thermal transfer element.
Yet another embodiment is an article having a substrate and a microstructured component having a surface defining microstructured features. The microstructured component is formed on the substrate by thermal transfer of at least a portion of a microstructured layer from a thermal transfer element.
A further embodiment is a method of making a thermal transfer element. A microstructured layer is formed on a substrate, optionally over a light-to-heat conversion layer, and with a surface defining microstructured features imposed on the microstructured layer. The microstructured features can be imposed on the microstructured layer by forming the layer on a substrate containing microstructured features or by modifying the surface of the layer after the layer has been formed. The microstructured layer forms at least a portion of the transfer unit of the thermal transfer element.
The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify these embodiments.